1. Field of the Invention
The present invention relates generally to a wireless power receiver and a method for controlling the same, and more particularly, to a wireless power receiver for suppressing ripple caused by load modulation and a method for controlling the same.
2. Description of the Related Art
Mobile terminals, such as mobile phones and Personal Digital Assistants (PDAs), are powered by a rechargeable battery.
Recently, wireless or contactless charging technologies have been developed and used to charge these rechargeable batteries. By using these wireless charging technologies, which use wireless power transmission/reception, a battery may be charged by merely placing a device, for example, a mobile phone, on a charging pad without connecting it to a separate charging connector.
These wireless charging technologies may be roughly classified into a coil-based electromagnetic induction scheme, a resonance scheme, and a Radio Frequency (RF)/microwave radiation scheme that transforms electric energy into microwaves and transmits the microwaves.
An electromagnetic induction-based power transmission method transmits power between a primary coil and a secondary coil. Specifically, an induced current is generated as a magnet moves around a coil, or vice versa. Based on this, a transmitter generates a magnetic field, and a receiver produces energy as a current is induced depending on changes in magnetic field. This phenomenon is referred to as magnetic induction, and a magnetic induction-based power transmission method has excellent energy transfer efficiency.
As to the resonance scheme, electricity is delivered wirelessly to electronic products that are several meters away from the charging device. The resonance scheme uses a resonance concept of physics that, if a tuning fork rings or resonates, a nearby wine glass may also ring at the same frequency. The resonance scheme causes electromagnetic waves containing electric energy to resonate, instead of the sound to resonate. However, the resonant electrical energy may be directly transferred only when there are devices having a resonant frequency.
A conventional wireless power receiver utilizes a load modulation scheme for communication with a wireless power transmitter. However, a ripple often occurs in an output voltage due to load modulation performed in the conventional wireless power receiver. The conventional wireless power receiver may include a regulator to reduce the ripple, but the total efficiency may be undesirably reduced by adding the regulator to wireless power receiver.